Vibratory compacting machines are commonly used in construction to compact material, such as soil, gravel, or asphalt. For example, vibratory compacting machines may be used to compact freshly laid asphalt, gravel, or soil for road construction, road maintenance, or budding construction purposes. Vibratory compacting machines typically include one or more compacting elements, such as a drum, a tire, or a plate, that is vibrated to apply compaction forces on the compactable material. A vibratory system may be housed within the compacting element to induce vibration of the compacting element. Such vibratory systems may include a shaft that rotates about a rotation axis of the compacting element, and an eccentric weight rotatably coupled to shaft that rotates with the shaft to cause vibration of the compacting element. The shaft and the eccentric may be rotated in a direction that correlates with the direction of travel of the compacting machine.
Vibratory compacting machines can control both the amplitude and the frequency of vibration of the vibratory system to adjust the degree of compaction. For instance, in U.S. Pat. No. 8,393,826, a key shaft engages a pair of inner and outer concentrically positioned eccentric weights to induce rotation of the inner eccentric weight with respect to the outer eccentric weight. Specifically, when the inner and outer eccentric weights are out of phase with each other (on opposite sides of the shaft axis), the vibratory system operates at a minimum amplitude, whereas when the inner and outer eccentric weights are in phase with each other (on the same side of the shaft axis), the vibratory system operates at maximum amplitude.
Although effective, the aforementioned systems do not address problems with decompaction of the compactable material. Decompaction may occur when the compacting machine exerts significant force on the compactable material after it has reached a certain compaction level, such that the compaction reverses and the compactable material begins to separate. When this occurs, the compaction process may need to be repeated to reestablish the compaction level that was lost, thereby adding to the total compaction time and decreasing the efficiency of the compaction process. Thus, there is a need for strategies for reducing or minimizing the decompaction of compactable materials when using vibratory compacting machines.